Flexible expandable stent

ABSTRACT

A stent for implanting in the body to hold open a blood vessel includes cells with facing loops and the curved flexible links disposed and adapted to cooperate so that, when unexpended, the stent can flex as it is moved through curved blood vessels to a site where it is to be expanded and so that, when the stent is expanded in a curved vessel, at that site, as compared to each other, cells on the outside of the curve are open in length, but narrow in width as compared to cells on the inside of the curve which are short in length but increased in width to result in a more constant stent cell area between the inside and the outside of the curve than would otherwise occur causing the stent, when coated with a medicine, to apply a more even dose to the inside wall of the lumen, avoiding the possibility that a toxic dose is supplied at one area while a less than effective dose is applied to another area.

RELATED APPLICATIONS

[0001] This application is a continuation of Ser. No. 09/337,629 filedJun. 21, 1999, which is a continuation of Ser. No. 09/026,099 filed Feb.19, 1998 (now U.S. Pat. No. 5,972,018), which is a continuation of Ser.No. 08/881,594 filed Jun. 24, 1997(now U.S. Pat. No. 5,843,120), whichis a continuation of Ser. No. 08/782,467 filed Jan. 10, 1997, nowabandoned, which is a continuation of Ser. No. 08/457,354, filed May 31,1995 (now U.S. Pat. No. 5,733,303), which is a continuation of Ser. No.08/282,181 filed Jul. 28, 1994 (now abandoned) and acontinuation-in-part of Ser. No. 08/213,272, filed Mar. 17, 1994 (nowU.S. Pat. No. 5,449,373).

FIELD OF THE INVENTION

[0002] The present invention relates generally to stents for implantinginto a living body.

BACKGROUND OF THE INVENTION

[0003] Various stems are known in the art wherein, for the presentapplication, the term “stent” indicates a device, made ofbody-compatible material, which is utilized to widen a blood vessel, orother orifice in the body, and to maintain the resultant size of thelumen. Typically, the stent is delivered to the desired location in thebody with an inflatable balloon and, when the balloon is inflated, thestem expands, thereby widening the orifice. Other mechanical deviceswhich cause expansion of the stent are also utilized.

[0004] Exemplary patents in the field of stents formed of wire are: U.S.Pat. No. 5,019,090 to Pinchuk, U.S. Pat. No. 5,161,547 to Tower, U.S.Pat. No. 4,950,227 to Savin, et al., U.S. Pat. No. 5,314,472 toFontaine, U.S. Pat No. 4,886,062 and U.S. Pat. No. 4,969,458 to Wiktorand U.S. Pat. No. 4,856,516 to Hillstead. Stems formed of cut stockmetal are described in: U.S. Pat. No. 4,733,665 to Palmaz, U.S. Pat. No.4,762,128 to Rosenbluth, U.S. Pat. No. 5,102,417 to Palmaz and Schatz,U.S. Pat. No. 5,195,984 to Schatz and WO 91FR013820 to Meadox.

[0005] The stents described in U.S. Pat. No. 5,102,417 to Palmaz andSchatz have expandable tubular grafts connected together with a flexibleconnector. The grafts are formed of a plurality of slots disposedparallel to the longitudinal axis of the tube. The flexible connectorsare helical connectors. Since the tubular grafts are relatively rigid,the flexible connectors are needed so that the stents can bend whenbeing fed through a curved blood vessel. When the stents of U.S. Pat.No. 5,102,417 expand, the grafts expand radially and, consequently,shrink longitudinally. However, at the same time, the helical connectorstwist. The twisting motion is most probably harmful to the blood vessel.

[0006] U.S. Pat. No. 5,195,984 to Schatz describes a similar stent butwith one straight connector, parallel to the longitudinal axis of thetubular grafts, between tubular grafts. The straight member removes thetwisting motion; however, it is not a very strong connector.

SUMMARY OF THE PRESENT INVENTION

[0007] In accordance with embodiments of the present invention, a stentfor implanting in the body to hold open a blood vessel, includes abody-compatible metal mesh defining a tube having adjacent contiguouscells, the cells having walls which are also the walls of adjacentcells. Each of the plurality of cells includes a pair of facing loops,each facing loop having a curved apex generally aligned along thelongitudinal axis. Each facing loop has a first end and a second endthat are generally aligned along the circumferential axis, each of thefacing loops adapted to open further upon radial expansion of the stentwhich tends to foreshorten the stent longitudinally. Each of theplurality of cells further includes a pair of curved flexible linkswhich connect the adjacent ends of the pair of facing loops to completeeach of the plurality of cells, the pair of curved flexible links madeof a metal which, upon expansion of the stent, bend to substantiallyoffset foreshortening along the longitudinal axis.

[0008] The pair of facing loops and the curved flexible links aredisposed and adapted to cooperate so that the tube, when unexpended, canflex as it is moved through curved blood vessels to a site where it isto be expanded and so that, when the stent is expanded in a curvedvessel, at that site, as compared to each other, cells on the outside ofthe curve are open in length, but narrow in width as compared to cellson the inside of the curve which are short in length but increased inwidth. This results in a more constant stent cell area between theinside and the outside of the curve than would otherwise occur.Consequently, when the stent is coated with a medicine the compensationresults in a more even dose being applied to the inside wall of thelumen, avoiding the possibility that a toxic dose is supplied at onearea while a less than effective dose is applied to another area

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The present invention will be understood and appreciated morefully from the following detailed description taken in conjunction withthe drawings in which:

[0010]FIG. 1 is an illustration of a patterned stent, constructed andoperative in accordance with a first preferred embodiment of the presentinvention;

[0011]FIG. 2 is an illustration of the pattern of the stent of FIG. 1;

[0012]FIG. 3 is an illustration of the stent of FIG. 1 in a bentposition;

[0013]FIG. 4 is an illustration of the stent of FIG. 1 in an expandedformat;

[0014]FIGS. 5A and 5B are illustrations of the changes in the patternsof the stent of FIG. 1 due to expansion;

[0015]FIG. 6 is a schematic illustration of a second embodiment of thepattern for a stent;

[0016]FIG. 7 is an illustration of a third embodiment of the pattern forthe stent; and

[0017]FIG. 8 is an illustration of the pattern of FIG. 7 in an expandedformat.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0018] Reference is now made to FIGS. 1-4 which illustrate a firstembodiment of a stent, constructed and operative in accordance with theprinciples of the present invention. FIG. 1 illustrates the stent in itsnon-expanded form, FIG. 2 illustrates the pattern of the stent, FIG. 3illustrates it in a partially bent position and FIG. 4 illustrates it inan expanded form As shown in FIG. 3, the stent 30 defines a longitudinalaperture 80 having a longitudinal axis or longitudinal extension 79.

[0019] The stent of the present invention is a tube whose sides areformed into a plurality of each of two orthogonal meander patterns whichpatterns are intertwined with each other. The term “meander pattern” istaken herein to describe a periodic pattern about center line and“orthogonal meander patterns” are patterns whose center lines areorthogonal to each other.

[0020] In the stent of FIGS. 1-4, the two meander patterns are labeled11 and 12 and they are most easily seen in FIG. 2. Meander pattern 11 isa vertical sinusoid having a vertical center line 9. Meander pattern 11has two loops 14 and 16 per period wherein loops 14 open to the rightwhile loops 16 open to the left. Loops 14 and 16 share common members 15and 17, where member 15 connects from one loop 14 to its following loop16 and member 15 connects from one loop 16 to its following loop 14.

[0021] Meander pattern 12 is an horizontal pattern having an horizontalcenter line 13. Meander pattern 12 also has loops, labeled 18 and 20,but between loops of a period is an extended straight section labeled22. Loops 18 open downwards and loops 20 open upwards.

[0022] Vertical meander pattern 11 is provided in odd and even (o and e)versions which are 180° out of phase with each other. Thus, each leftopening loop 16 of meander pattern 11 o faces a right opening loop 14 ofmeander pattern 11 e and a right opening loop 14 of meander pattern 11 ofaces a left opening loop 16 of meander pattern 11 e.

[0023] Horizontal meander pattern 12 is also provided in odd and evenforms. The straight sections 22 of horizontal meander pattern 12 eintersect with every third common member 17 of vertical meander pattern11 e. The straight sections 22 of horizontal meander pattern 12 ointersect with every third common member 15 of vertical meander pattern11 e, beginning with the common member 15 two after an intersectedcommon member 17. The result is a full loop 14 between meander patterns12 e and 12 o and a full loop 16 between meander patterns 12 o and 12 e.

[0024] Returning to FIG. 1, the pattern of FIG. 2 is formed into a tube30 of an easily deformable material, such as a metal. Due to the twomeander patterns, the stent of FIG. 1, when attached over a catheterballoon, is flexible and can therefore be easily dragged through curvedblood vessels. An example of the way in which the stent of FIG. 1 bendsis illustrated in FIG. 3.

[0025] In FIG. 3, the stent begins to bend at the point marked A in thedirection marked by arrow 40. As the stent begins to curve, the sectionmarked I becomes the inside of the curve while the section marked Obecomes the outside of the curve. The inside of the curve I is shortenedvis-a-vis the outside of the curve O.

[0026] During bending, the loops 14-20 to the right of the point Achange shape in order to compensate for the differences in lengthbetween the inside and outside curves. For example, loops 18 i and 20 inear the inside of the curve are closer together than loops 18 o and 20o on the outside of the curve, which expand. Loops 14 i and 16 i nearthe inside I are compressed while the loops 14 o and 16 o closer to theoutside O of the curve are expanded.

[0027] As can be seen, both meander patterns 11 and 12 are involved inthe bending. Although not shown, it will be appreciated that the stentof FIGS. 1-4 can bend in any direction and in more than one direction atany time.

[0028]FIG. 4 illustrates the stent of FIG. 1 in its expanded form. Whenthe stent expands, both meander patterns 11 and 12 expand (i.e. allloops 14-20 open up). As can be seen, the expanded stent has two typesof enclosed spaces, a large space 42 between meander patterns 12 o and12 e and a small space 44 between meander patterns 12 e and 12 o. As canalso be seen, each large space 42 has two loops 14 on its left side andtwo loops 16 on its fight side. The large spaces between verticalmeander patterns 11 e and 11 o, which are labeled 42 a, have loops 18 attheir tops and bottoms while the large spaces between vertical meanderpatterns 11 o and 11 e, which are labeled 42 b, have loops 20 at theirtops and bottoms. Similarly for small spaces 44 a and 44 b.

[0029] It is noted that, due to the orthogonal meander patterns 11 and12, the stent of FIG. 1 does not significantly shrink during expansion.This is illustrated in detail in FIGS. 5A and 5B to which reference isnow made. FIG. 5A illustrates the movement, during expansion, of onevertical meander pattern 11 and FIG. 5B illustrates the movement, duringexpansion, of one horizontal meander pattern 12. The original patternsare shown with solid lines and the expanded patterns are shown withdashed lines.

[0030] The vertical meander pattern 11 of FIG. 5A expands by wideningits loops 14 and 16. As a result, the vertical meander pattern 11 growsvertically by an amount 2*h₁ per loop. However, it also shrinkshorizontally, by an amount 2*d₁. Similarly, the horizontal meanderpattern 12 of FIG. 5B expands by widening its loops 18 and 20. As aresult, the horizontal meander pattern 12 grows horizontally by anamount 2*d₂ per loop. However, it also shrinks vertically, by an amounth₂. Thus, the vertical growth of the vertical meander pattern 11compensates, at least partially, for the vertical shrinkage of thehorizontal meander pattern 12, and vice versa. It is noted that the endportions of any stent are only partially compensated and therefore, mayshrink somewhat.

[0031] It will be appreciated that the two orthogonal meander patterns11 and 12 and the compensation they provide to each other providesflexibility to the unexpended stent of FIG. 1. However, when the stentis expanded, the changes in each of loops 14 and 16 provide rigidity tothe resultant stent and thus, enable the stent to maintain a bloodvessel at a desired inner diameter.

[0032] The stent of the present invention can be manufactured from flatmetal which is etched into the pattern of FIG. 2. The etched metal isthen bent to form the tube 30. Alternatively, the pattern of FIG. 2 canbe manufactured from welded or twisted wire.

[0033] It will be appreciated that the stent of the present inventioncan be made from metal and/or wire. Additionally, it can be plated witha protective material, embedded with a medicine, and/or covered with amaterial which can fill in the spaces 42 and 44.

[0034] It will be appreciated that the present invention encompasses allstents manufactured with a pattern formed of two meander patterns,orthogonal or otherwise. Another exemplary pattern, also with orthogonalmeander patterns, is provided herein wherein FIG. 6 is a schematicversion and FIG. 7 is a more rounded version. FIG. 8 shows the patternof FIG. 7 in an expanded format. The pattern of FIGS. 6 and 7 is similarto that shown in FIG. 2 except that it has more horizontal meanderpatterns 12 and they are of one kind, rather than being even and odd asin FIG. 2.

[0035] As can be seen in both FIGS. 6 and 7, there are two types ofvertical meander patterns 11 e and 11 o which are 180° out of phase witheach other. The horizontal meander patterns 12 connect with every line15 of vertical meander pattern 11 e.

[0036]FIG. 8 illustrates the pattern of FIG. 7 is an expanded format.Since there are no even and odd horizontal meander patterns, in theexpanded format of FIG. 8, there are no large and small spaces. Instead,all spaces are of the same size, i.e., the stent is comprised of aplurality of spaces or cells 50 defining a uniform cellular structure.

[0037] As shown in FIGS. 3, 7 and 8, Applicants' invention can also bedescribed as an expandable stent defining a longitudinal aperture 80having a longitudinal axis or extension 79 and a circumferential axis orextension 105, including a plurality of flexible connected cells 50 witheach of the flexible cells 50 having a first longitudinal end 77 and asecond longitudinal end 78. Each cell 50 also is provided with a firstlongitudinal apex 100 disposed at the first longitudinal end 77 and asecond longitudinal apex 104 disposed at the second longitudinal end 78.Each cell 50 also includes a first member 51 having a longitudinalcomponent having a first end 52 and a second end 53; a second member 54having a longitudinal component having a first end 55 and a second end56; a third member 57 having a longitudinal component having a first end58 and a second end 59; and a fourth member 60 having a longitudinalcomponent having a first end 61 and a second end 62. The stent alsoincludes a first loop 63 defining a first angle 64 disposed between thefirst end 52 of the first member 51 and the first end 55 of the secondmember 54.

[0038] A second loop 65 defining a second angle 66 is disposed betweenthe second end 59 of the third member 57 and the second end 62 of thefourth member 60 and is disposed generally opposite to the first loop63. A first flexible compensating member or flexible link 67 having afirst end 68 and a second end 69 is disposed between the first member 51and the third member 57 with the first end 68 of the first flexiblecompensating member or flexible link 67 communicating with the secondend 53 of the first member 51 and the second end 69 of the firstflexible compensating member or flexible link 67 communicating with thefirst end 58 of the third member 57. The first end 68 and the second end69 are disposed a variable longitudinal distance 70 from each other.

[0039] A second flexible compensating member 71 having a first end 72and a second end 73 is disposed between the second member 54 and thefourth member 60. The first end 72 of the second flexible compensatingmember or flexible link 71 communicates with the second end 56 of thesecond member 54 and the second end 73 of the second flexiblecompensating member or flexible link 71 communicates with the first end61 of the fourth member 60. The first end 72 and the second end 73 aredisposed a variable longitudinal distance 74 from each other.

[0040] In a preferred embodiment, the first and second flexiblecompensating member or flexible links 67 and 71 are arcuate. The fistand second flexible compensating member or flexible links 67 and 71 aredifferentially extendable or compressible when the stent is bent in acurved direction away from the longitudinal axis 79 of the aperture 80.(Shown in FIG. 3.) The first member 51, second member 54, third member57, and fourth member 60 and the first loop 63 and the second loop 65and the first flexible compensating member or flexible link 67 and thesecond flexible compensating member or flexible link 71 are disposed sothat as the stent is expanded the distance between the first flexiblecompensating member or flexible link 67 and the second flexiblecompensating member or flexible link 71 increases and the longitudinalcomponent of the first member 51, second member 54, third member 57 andfourth member 60 decreases while the first loop 63 and the second loop65 remain generally opposite to one another, the ends 68 and 69 of thefirst flexible compensating member or flexible link 67 and the ends 72and 73 of the second flexible compensating member or flexible link 71open so as to increase the variable longitudinal distance 70 between thefirst end 68 and the second end 69 of the first flexible compensatingmember or flexible link 67 and so as to increase the variablelongitudinal distance 74 between the first end 72 and the second end 73of the second flexible compensating member or flexible link 71. Thiscompensates for the decreasing of the longitudinal component of thefirst member 51, second member 54, third member 57, and fourth member 60and substantially lessens the foreshortening of the stent upon itsexpansion.

[0041] In a preferred embodiment, and as shown in FIG. 5A, the flexiblecompensating member or flexible links 67 and 71 compensate in an amountthat is substantially equal to the amount that the stent foreshortens.As shown in FIGS. 7 and 8, the first flexible compensating member orflexible link 67 and the second flexible compensating member or flexiblelink 71 in each cell 50 of each row or band of cells 101, 102 and 103,serve to flexibly connect other cells 50 in adjacent rows or bands 102,103, and 104 which themselves have first and second compensating members67 and 71.

[0042] As shown in FIG. 7, the first flexible compensating member orflexible links 67 and 71 in row or band 101 serve to flexibly connectthe cells 50 in adjacent rows or bands 102 and 103. As shown in FIGS. 7and 8, a portion of the flexible member 67 or 71 disposed between thefirst ends 68 and 72 and the second ends 69 and 73 may be provided witha width that is smaller than the width of the apices 100 and 104 towhich they are attached.

[0043] It will be appreciated by persons skilled in the art that thepresent invention is not limited to what has been particularly shown anddescribed hereinabove. Rather the scope of the present invention isdefined by the claims which follow:

What is claimed is:
 1. A stent for implanting in the body to hold open ablood vessel, comprising: a. a body-compatible metal mesh defining atube having adjacent contiguous cells, the cells having walls which arealso the walls of adjacent cells, each of the plurality of cellsincluding a pair of facing loops, each facing loop having a curved apexgenerally aligned along the longitudinal axis, and each facing loophaving a first end and a second end that are generally aligned along thecircumferential axis, each of the facing loops adapted to open furtherupon radial expansion of the stent which tends to foreshorten the stentlongitudinally, b. each of the plurality of cells further including apair of curved flexible links which connect the adjacent ends of thepair of facing loops to complete each of the plurality of cells, thepair of curved flexible links made of a metal which, upon expansion ofthe stent, bend to substantially offset foreshortening along thelongitudinal axis, and c. said pair of facing loops and said curvedflexible links disposed and adapted to cooperate so that the tube, whenunexpended, can flex as it is moved through curved blood vessels to asite where it is to be expanded and so that, when the stent is expandedin a curved vessel, at that site, as compared to each other, cells onthe outside of the curve are open in length, but narrow in width ascompared to cells on the inside of the curve which are short in lengthbut increased in width.
 2. A stent according to claim 1 wherein on theoutside of the curve, the curved flexible links are open and the facingloops are closed as compared to the inside of the curve, where theflexible links are closed and the facing loops are open.
 3. A stentaccording to claim 1 wherein compensation, which occurs when cells onthe outside of the curve are open in length, but narrower in width ascompared to cells on the inside of the curve, which are shorter inlength but increased in width, results in a more constant density ofstent element area between the inside and the outside of the curve thanwould otherwise occur.
 4. A stent according to claim 1 whereincompensation, which occurs when cells on the outside of the curve areopen in length, but narrower in width as compared to cells on the insideof the curve, which are shorter in length but increased in width,results in a more constant stent cell area between the inside and theoutside of the curve than would otherwise occur.
 5. A stent according toclaim 3 wherein said stent is coated with a medicine and saidcompensation results in a more even dose being applied to the insidewall of the lumen, avoiding the possibility that a toxic dose issupplied at one area while a less than effective dose is applied toanother area
 6. A stent according to claim 4 wherein said stent iscoated with a medicine and said compensation results in a more even dosebeing applied to the inside wall of the lumen, avoiding the possibilitythat a toxic dose is supplied at one area while a less than effectivedose is applied to another area
 7. The stent of claim 1, positioned on aballoon which upon expansion causes the stent to expand to hold open theblood vessel.
 8. The expanded stent of claim 1, in which the expandedstent has approximately the same longitudinal length as the stent hadprior to expansion.
 9. A balloon-expandable stent defining alongitudinal aperture, said stent consisting essentially of: a. aplurality of flexible connected cells, each of said flexible cellscomprising: i. a first member having a longitudinal component having afirst end and a second end; ii. a second member having a longitudinalcomponent having a first end and iii. a third member having alongitudinal component having a first end and a second end; iv. a fourthmember having a longitudinal component having a first end and a secondend; v. a first loop defining a first angle disposed between said firstend of said first member and said first end of said second member; vi. asecond loop defining a second angle disposed between said second end ofsaid third member and said second end of said fourth member, anddisposed generally opposite to said first loop so that said first angleand said second angle open toward each other; vii. a first flexiblecompensating member having a first end and a second end disposed betweensaid first member and said third member, said first end of said firstflexible compensating member communicating with said second end of saidfirst member and said second end of said first flexible compensatingmember communicating with said first end of said third member, saidfirst and said second ends disposed a variable longitudinal distancefrom each other; viii. a second flexible compensating member having afirst end and a second end disposed between said second member and saidfourth member, said first end of said second flexible compensatingmember communicating with said second end of said second member and saidsecond end of said second flexible compensating member communicatingwith said first end of said fourth member, said first and said secondends disposed a variable longitudinal distance from each other, saidfirst and said second flexible compensating member differentiallyextendable or compressible when said stent is bent in a curved directionaway from the longitudinal axis of said aperture; and ix. said first,said second, said third, and said fourth members and said first and saidsecond loops, and said first and said second flexible compensatingmember disposed so that as said stent is balloon-expanded from adelivery diameter to a deployment diameter the distance between saidfirst and said second flexible compensating member increases and thelongitudinal component of said first, second, third and fourth membersdecreases while said first and said second loops remain generallyopposite to one another, the ends of said first and said second flexiblecompensating member open so as to increase said variable longitudinaldistance between said first and said second ends of said first flexiblecompensating member and so as to increase said variable longitudinaldistance between said first and said second ends of said second flexiblecompensating member so as to compensate for the decreasing of thelongitudinal component of said first, second, third, and fourth membersand substantially lessen the foreshortening of said stent upon itsexpansion; and b. said first and second loops and said flexiblecompensating member disposed and adapted to cooperate so that the tube,when unexpended, can flex as it is moved through curved blood vessels toa site where it is to be expanded and so that, when the stent isexpanded in a curved vessel, at that site, as compared to each other,cells on the outside of the curve are open in length, but narrow inwidth as compared to cells on the inside of the curve which are short inlength but increased in width.
 10. A stent according to claim 9 whereinon the outside of the curve, the flexible compensating members open upand the first and second loops close down, and on the inside of thecurve, the flexible compensating members close down and the first andsecond loops open up.
 11. A stent according to claim 9 whereincompensation, which occurs when cells on the outside of the curve openin length, but narrow in width and cells on the inside of the curveshorten in length but thicken in width, results in a more constantdensity of stent element area between the inside and the outside of thecurve than would otherwise occur.
 12. A stent according to claim 9wherein compensation, which occurs when cells on the outside of thecurve open in length, but narrow in width and cells on the inside of thecurve shorten in length but thicken in width, results in a more constantstent cell area between the inside and the outside of the curve thanwould otherwise occur.
 13. A stent according to claim 12 wherein saidstent is coated with a medicine and said compensation results in a moreeven dose being applied to the inside wall of the lumen, avoiding thepossibility that a toxic dose is supplied at one area while a less thaneffective dose is applied to another area.
 14. A stent according toclaim 11 wherein said stent is coated with a medicine and saidcompensation results in a more even dose being applied to the insidewall of the lumen, avoiding the possibility that a toxic dose issupplied at one area while a less than effective dose is applied toanother area.
 15. A balloon-expandable stent, consisting substantiallyof: a. flexible cells disposed about the circumference of the stent,each of said cells having a first longitudinal end and a secondlongitudinal end and an upper end and a lower end, each of said cellsconsisting essentially of i. a first pair of members connected by anarea of inflection generally disposed at said first longitudinal end ofeach of said cells; ii. a second pair of members connected by an area ofinflection generally disposed at said second longitudinal end of each ofsaid cells; and iii. a first flexible compensating member disposedbetween said first and second pair of members at said upper end of eachof said cells; iv. a second flexible compensating member disposedbetween said first and second pair of members at said lower end of eachof said cells; b. wherein upon bending of the stent the flexiblecompensating members on the outside of the bend lengthen in thelongitudinal direction and the flexible compensating members on theinside of the bend shorten in the longitudinal direction; c. whereinupon expansion of the stent by a balloon from a delivery diameter to adeployment diameter, the flexible compensating members lengthen in thelongitudinal direction to compensate for the tendency of the stent toforeshorten; and d. wherein, when the expanded stent is in a curvedlumen, on the outside of the bend, the first and second pairs of memberscome closer together in the circumferential direction, as compared tothe inside of the bend, where the first and second pairs of membersseparate in the circumferential direction.
 16. A stent according toclaim 15 wherein compensation which occurs when the first and secondpairs of members come closer together in the circumferential directionon the outside and the first and second pairs of members separate in thecircumferential direction on the inside compensates respectively for theshortening and lengthening of the flexible compensating members toresult in a more constant density of stent element area between theinside and the outside of the curve than would otherwise occur.
 17. Astent according to claim 15 wherein compensation which occurs when thefirst and second pairs of members come closer together in thecircumferential direction on the outside and the first and second pairsof members separate in the circumferential direction on the insidecompensates respectively for the shortening and lengthening of theflexible compensating members to result in a more constant stent cellarea between the inside and the outside of the curve than wouldotherwise occur.
 18. A stent according to claim 16 wherein said stent iscoated with a medicine and said more constant density of stent elementsresults in a more even dose being applied to the inside wall of thelumen, avoiding the possibility that a toxic dose is supplied at onearea while a less than effective dose is applied to another area
 19. Astent according to claim 17 wherein said stent is coated with a medicineand said more constant density of stent elements results in a more evendose being applied to the inside wall of the lumen, avoiding thepossibility that a toxic dose is supplied at one area while a less thaneffective dose is applied to another area
 20. A flexible,balloon-expandable stent having a longitudinal axis, consistingessentially of: a. a plurality of flexible cells, each of said flexiblecells consisting essentially of: i. a first pair of members connected byan area of inflection defining a right-facing loop; ii. a second pair ofmembers connected by an area of inflection defining a left-facing loopthat faces the right-facing loop; iii. a first flexible link connectingthe top of said first pair of members to the top of said second pair ofmembers; and iv. a second flexible link connecting the bottom of saidfirst pair of members to the bottom of said second pair of members; b.wherein said flexible cells are adapted so that said stent prior toexpansion is bendable in substantially any direction without affectingthe structural or functional integrity of said stent, c. wherein saidflexible cells are adapted so that upon the expansion of said stent by aballoon from a delivery diameter to a deployment diameter, said firstand second pairs of members shorten in a longitudinal direction and saidflexible links lengthen in the longitudinal direction to compensate forsaid first and second pairs of members shortening in the longitudinaldirection and for the tendency of said stent to foreshorten, and d.wherein said flexible cells are further adapted to impart rigidity tosaid stent in an amount sufficient to support a lumen when said stent isexpanded; and e. wherein said right and left facing loops and saidflexible links are disposed and adapted to cooperate so that the tube,when unexpended, can flex as it is moved through curved blood vessels toa site where it is to be expanded and so that, when the stent isexpanded in a curved vessel, at that site, as compared to each other,cells on the outside of the curve are open in length, but narrow inwidth as compared to cells on the inside of the curve which are short inlength but increased in width.
 21. A stent according to claim 20,wherein on the outside of the curve, the curved flexible links open upand the loops close down, and on the inside of the curve, the flexiblelinks close down and the loops open up.
 22. A stent according to claim20 wherein compensation, which occurs when cells on the outside of thecurve open in length, but narrow in width and cells on the inside of thecurve shorten in length but thicken in width, results in a more constantdensity of stent element area between the inside and the outside of thecurve than would otherwise occur.
 23. A stent according to claim 20wherein compensation, which occurs when cells on the outside of thecurve open in length, but narrow in width and cells on the inside of thecurve shorten in length but thicken in width, results in a more constantstent cell area between the inside and the outside of the curve thanwould otherwise occur.
 24. A stent according to claim 22 wherein saidstent is coated with a medicine and said more constant density of stentelements results in a more even dose being applied to the inside wall ofthe lumen, avoiding the possibility that a toxic dose is supplied at onearea while a less than effective dose is applied to another area.
 25. Astent according to claim 23 wherein said stent is coated with a medicineand said more constant density of stent elements results in a more evendose being applied to the inside wall of the lumen, avoiding thepossibility that a toxic dose is supplied at one area while a less thaneffective dose is applied to another area.
 26. An expandable stent forsupporting a vessel, wherein in the expanded and deployed state, thestent consists of: a. first meander patterns having loops, the firstmeander patterns having axes extending circumferentially; and b. secondmeander patterns having loops, the second meander patterns having axesextending horizontally, c. wherein the first and second meander patternsare intertwined to form a tubular structure; d. wherein the firstmeander patterns are connected to the second meander patterns so as toleave at least one loop of the second meander patterns between each pairof adjacent first meander patterns; e. wherein the second meanderpatterns are connected to the first meander patterns so as to leave twoloops of the first meander patterns between each pair of adjacent secondmeander patterns; and f. wherein said first and second meander patternsare adapted to cooperate so that, when the expanded stent is in a curvedvessel, on the outside of the curve, a circumferential shrinkage andhorizontal growth of the loops in said first meander patternsubstantially compensates for a horizontal growth and circumferentialcompression of the loops in said second meander pattern and vice versaon the inside of the curve.
 27. A stent according to claim 26, whereinon the outside of the curve, the loops in said second meander patternopen up and the loops in the first meander pattern close down, and onthe inside of the curve, the loops in said second meander pattern closedown and the loops in the first meander pattern open up.
 28. A stentaccording to claim 26 wherein the compensation maintains a density ofstent element area which is more constant on the inside and on theoutside of the curve than it would without the compensation.
 29. A stentaccording to claim 26 wherein the compensation maintains a stent areawhich is more constant on the inside and on the outside of the curvethan it would without the compensation.
 30. A stent according to claim28 wherein said stent is coated with a medicine and said more constantdensity of stent elements results in a more even dose being applied tothe inside wall of the lumen, avoiding the possibility that a toxic doseis supplied at one area while a less than effective dose is applied toanother area
 31. A stent according to claim 29 wherein said stent iscoated with a medicine and said more constant density of stent elementsresults in a more even dose being applied to the inside wall of thelumen, avoiding the possibility that a toxic dose is supplied at onearea while a less than effective dose is applied to another area
 32. Thestent according to claim 26, wherein the shape of the loops providesrigidity to the stent to enable the stent to maintain a blood vessel ata desired inner diameter.
 33. The stent according to claim 26, whereinthe stent defines a plurality of enclosed spaces, with each longitudinalend of the enclosed space being formed by loops of the first meanderpattern.
 34. The stent according to claim 33 wherein the enclosed spacesare substantially the same size.
 35. A stent formed of a tube having apatterned shape consisting of a. even first meander patterns having axesextending [in a first direction] circumferentially; b. odd first meanderpatterns having axes extending [in a first direction] circumferentially,wherein the odd first meander patterns are 180° out of phase with theeven first meander patterns and occur between every two even firstmeander patterns; c. second meander patterns having axes extending [in asecond direction different from the first direction] horizontally, [and]the second meander patterns [are] intertwined with the even and oddfirst meander patterns to form a generally uniform distributedstructure; d. wherein the first and second meander patterns have loops,e. wherein the even and odd first meander patterns are interconnected toleave a portion of the second meander pattern between adjacent even andodd first meander patterns, f. wherein the portion of the second meanderpattern between adjacent even and odd first meander patterns adapted tocompensate for the tendency of the loops of the first meander toforeshorten when the stent is expanded, g. wherein the second meandersare interconnected to leave two loops of the first meander patternbetween each pair of second meander pattern, and h. wherein the portionof the second meander pattern between adjacent even and odd firstmeander patterns and loops of the first meander pattern are adapted tocooperate so that, when the expanded stent is in a curved vessel, on theoutside of the curve, a circumferential shrinkage and horizontal growthof the loops in said first meander pattern substantially compensates fora horizontal growth and circumferential compression of the portion ofthe second meander pattern between adjacent even and odd first meanderpatterns and vice versa on the inside of the curve.
 36. A stentaccording to claim 35, wherein on the outside of the curve, the portionof the second meander pattern between adjacent even and odd firstmeander patterns includes at least one loop and the loops in said secondmeander pattern open up and the loops in the first meander pattern closedown, and on the inside of the curve, the loops in said second meanderpattern close down and the loops in the first meander pattern open up.37. A stent according to claim 35 wherein the compensation maintains adensity of stent element area which is more constant on the inside andon the outside of the curve than it would without the compensation. 38.A stent according to claim 35 wherein the compensation maintains a stentarea which is more constant on the inside and on the outside of thecurve than it would without the compensation.
 39. A stent according toclaim 37 wherein said stent is coated with a medicine and said moreconstant density of stent elements results in a more even dose beingapplied to the inside wall of the lumen, avoiding the possibility that atoxic dose is supplied at one area while a less than effective dose isapplied to another area
 40. A stent according to claim 38 wherein saidstent is coated with a medicine and said more constant density of stentelements results in a more even dose being applied to the inside wall ofthe lumen, avoiding the possibility that a toxic dose is supplied at onearea while a less than effective dose is applied to another area
 41. Thestent according to claim 35, wherein changes in the shape of the loopsprovide rigidity to the stent upon expansion to enable the stent tomaintain a blood vessel at a desired inner diameter.